Table 2. Descriptive statistics of Little's irregularity index (LII) at five assessment times in the three groups and the results of significance test†.

† Employing one-way ANOVA test or Kruskal-Wallis test, SD: Standard Deviation, Min: minimum, Max: maximum, CI: confidence interval, T0: before the beginning of orthodontic treatment, T1: after 1 month, T2: after 2 months, T3: after 3 months, T4: at the end of the leveling and alignment phase, Group 1: traditional brackets group, Group 2: self-ligating brackets group, Group 3: self-ligating brackets + flapless piezocision group, NS: there was no statistically significant difference at P > 0.05, ***: there was a statistically significant difference at P < 0.001

ANOVA: analysis of variance

Time	Group	Mean	SD	Min	Max	95% CI for difference		P-value	Significance
						Lower bound	Upper bound
T0	Group 1	12.28	1.16	10.00	14.40	11.73	12.82	0.466	NS
	Group 2	12.13	1.06	10.00	14.00	11.61	12.64
	Group 3	12.58	1.19	10.60	14.70	12.00	13.16
T1	Group 1	9.82	1.06	7.90	11.60	9.32	10.31	<0.001	***
	Group 2	8.06	0.60	6.90	8.80	7.77	8.35
	Group 3	6.66	1.12	5.30	8.90	6.12	7.20
T2	Group 1	7.00	0.92	5.50	8.90	6.56	7.43	<0.001	***
	Group 2	4.85	0.56	3.70	5.70	4.58	5.12
	Group 3	2.68	0.69	1.00	3.90	2.34	3.02
T3	Group 1	4.45	0.71	3.10	5.80	4.11	4.79	˂0.001	***
	Group 2	2.65	0.73	1.00	3.90	2.30	3.01
	Group 3	0.42	0.76	0.00	2.10	0.05	0.79
T4	Group 1	0.27	0.60	0.00	2.20	-0.00	0.55	0.666	NS
	Group 2	0.17	0.54	0.00	2.00	-0.08	0.44
	Group 3	0.14	0.42	0.00	1.50	-0.06	0.34